Manhole frame and cover



.June 1.1, 1935. w E RMAN 2,004,335

MANHOLE FRAME AND fJOVER Filed March ,30, 1929 Iwuezzf 7 Patented June 11, 1935 UNITED STATES PATENT OFFICE 2,004,335 MANHOLE FRAME AND COVER MichaelW. Merriman, Cleveland, Ohio Application March 30, 1929, Serial No. 351,263

4 Claims.

This invention relates to improvements in manhole frames and covers, and a method of casting the same whereby true and accurate engaging surfaces between the frame and cover are provided without machining, and whereby the metal at these surfaces is hardened so as not to be worn down materially by the vibration and other relative movements between the frame and cover, due to the passage of. traffic thereover.

Another object is .to improve the frame of the manhole by hardening that portion thereof which has to withstand the heavy blows of traffic.

Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawing, in which:

Fig. 1 is a plan View of a manhole frame and cover in which the invention may be incorporated. I Fig. 2 is a vertical central sectional view of the same.

Fig. 3 is a. fragmental sectional view, more or less diagrammatic in character, illustrating a method of casting the frame member in accordance with the invention.

In the drawing, a manhole frame I 0 of circular contour is illustrated, this frame having a bottom flange II which is connected with the upstanding wall of the frame by vertical webs I2. This frame is intended and adapted to be set into, a street pavement, the upper surface I3 being exposed and being substantially flush with the surface of the pavement.

On the innerside of the frame, somewhere below the top thereof, there is formed an integral ledge I4. The upper periphery of this ledge is separated from the manholeof the frame by an annular groove I5. The metal at and just below the top surface I6 of the ledge is chilled. This surface constitutes the seat for the cover. The

metal at and just below the surface I3 is also chilled.

A circular cover I1, which is deepened at the center and periphery, is formed to fit within the frame, suitable sideclearance being provided so as to make the removal of the cover a matter merely of lifting the same. I The lower peripheral surface I! of the cover is formed to fit upon the seat I6, these two surfaces being preferably fiat or conical. The metal of the cover at the surface I 8 is chilled.

In Fig. 3 I have indicated at I9 the sand of a mold for casting the frame member III. In this figure a fragment of the block pattern is shown at 20. It is placed in the flask right side up.

. curately maintained surfaces of the chills, are

Upon the surfaces of the pattern which correspond to surfaces I3 and I6 of the casting are placed ring-shaped iron chills 2| and 22 respectively. The flask is then filled with sand and tamped, after which it is inverted, the pattern 5 withdrawn, and a sand core shaped to produce the internal surface of the frame inserted. When themetal is poured into the mold, that portion of it which comes in contact with the chills, naturally conforms exactly with the surfaces of the chills and, of course, is hardened. The cover I! is cast in a similar manner, except that one chill ring only is employed since there is butone chilled surface to produce.

I exercise considerable care in the making of the chill 22 and that for the surface I8, to insure the production of true and accurate surfaces for contact with themolten iron, and I subject them to inspection after each casting operation in order to make sure that they remain accurate. Those which become warped in use are either refinished or discarded. Hence, the surfaces I6 and I8 of the two castings which have been formed by engagement with themthemselves accurate and true, and a nice fit is insured. Accordingly, when a vehicle v passes over the cover, there is very little, if any, movement, and no audible noise. Wear is negligible both because of the absence of movement and because of the hardness of the engaging surfaces. The groove I 5 is ofsome importance in the casting of the frame member, inasmuch as it separates the chilled cover seat from the main wall of the casting.

While, in the foregoing specification, I have described the invention with reference to a manhole frame and cover, it is obviously applica-v ble to other articles of a more or less similar nature, particularly those inwhich an accurate seating of the cover is desirable.

Having thus described my invention, I claim:

1. In combination, a frame comprising an annular cover seat of chilled iron, an enclosing wall surrounding said seat, said wall being spaced fromthe seat, and a cover having an annular nular cover seat of chilled iron, and a cover having an annular chilled iron surface formed for engagement with said seat, whereby hardened, accurate engaging surfaces may be provided.

MICHAEL W. MERRIMAN. 

